NO_2体系的分析势能函数研究（一）

ANALYTICAL POTENTIAL ENERGY FUNCTION FOR THE GROUND STATE (X￣2A_1) OF NO_2(Ⅰ)

由多体项展式方法导出ＮＯ２体系的分析势能函数。提出对称性关联的方向性原则，正确地判断了离解极限。用开关函数解决了离解极限中出现激发态原子的问题，使势能表面准确地再现了ＮＯ２（Ｘ２Ａ１）平衡结构和ＯＮＯ（２πｕ）线性鞍点，并且，预测出过氧化氮ＮＯＯ（Ｃ∞ｖ）鞍点结构。

Analytical potential energy function for the ground state X2A1 of NO2 has been derived using many-body expansion method. The precent peper suggest a rule called the directianality of sym metry correlation, which correctly determines the dissociation limits, where the nitrogen atom N of NO2 can be both ground state 4 Su in the asymptotic approximation NO2(X2A1 )→O(3Pg) +NO (X2π)→N(4Su ) +2O (3Pg) and excited state 2 Du in the asymptotic approximation NO2 (X2A1)→ N (2 Du)+O2 (X3∑). therefore,the switch function is needed to consider this situation. Then,the potential energy function is quite accurate in rationalizing the equilibrium geometry of NO2 (X2A1)and ONO(2π),and predicting the saddle point NOO(C∞h).